Cytokeratin expression patterns of gastric carcinomas according to Lauren and Goseki classification

The Goseki system is a new gastric carcinoma classification system that classifies gastric carcinomas as grade I (intestinal type), grade II (mucinous type), grade III (mucin-poor, diffuse infiltrating type), and grade IV (signet ring cell type). The main advantage of the Goseki classification may be to separate these distinct entities into different groups. CK7 is not observed in normal gastric mucosa but can be detected in chronically inflamed gastric mucosa and coexists with incomplete intestinal metaplasia. CK20 can be observed in the superficial foveolar epithelium and mature goblet cells. The aim of this study was to examine the cytokeratin expression profiles in gastric carcinomas that are classified according to both the Goseki and Lauren systems. CK7, CK8, CK19, and CK20 were applied to the paraffin sections of 66 gastric carcinoma cases. The cytokeratin expression patterns were grouped as CK20+/CK7+, CK20+/CK7-, CK20-/CK7+, or CK20-/CK7-. The results were examined statistically. CK20 immunoreactivity was observed in 18%, 24%, and 31% of grade I, III, and IV cases, respectively. The CK20+/CK7- pattern was observed in 20% of the grade IV and 66.7% of the grade II carcinomas and was not observed in grade I or grade III tumors (P<0.0001). Goseki grade III and IV carcinomas originate from superficial gastric mucosa, but grade III carcinomas are poorly differentiated. Goseki grade II carcinomas have a specific immunophenotype other than intestinal-type gastric tumors. The Goseki classification seems to be superior in identifying poorly and well-differentiated forms of diffuse infiltrating carcinomas and mucinous carcinomas.